Esters of thiosulfonic acids as antifoggants



3,047,393 ESTERS F THIGSULFONIC ACIDS AS ANTIFOGGANTS Arthur H. Herz andFrank 1). Allen, Rochester, N.Y., as-

signors to Eastman Kodak Company, Rochester, N.Y.,

a corporation of New Jersey N0 Drawing. Filed Jan. 11, 1960, Ser. No.1,408 13 Claims. (Cl. 96-409) This invention relates to thestabilization of photographic silver halide emulsions, and moreparticularly, to a method of inhibiting development of spontaneous fogwithout adversely affecting the sensitivity of the photographic silverhalide emulsions.

It is well known that photographic emulsions on storage tend to losesensitivity and to become spontaneously developable without exposure tolight. There is normally a detectable amount of the silver salt reducedduring development in the areas where no exposure was given; this iscommonly called fog, and sometimes called chemical fog where it isnecessary to distinguish between it and the effects of accidentalexposure to radiation; in this invention, we are not concerned with thelatter.

Fog depends both on the emulsion and the conditions of development; fora given emulsion it increases With the degree of development. Withconstant development conditions, it tends to increase with time,temperature and relative humidity of storage conditions; it is commonpractice to make accelerated tests of the stability of photographicemulsions by storage at increased temperature or humidity, or both. Itis, of course, desirable to have emulsions as stable as possible underthe conditions of high temperature and humidity which may occur intropical climates, for example. Fog usually appears over the whole areaof the sensitive coating, but when severe, it frequently is non-uniform.Fog may also be caused by exposure to chemicals, for example, hydrogensulfide and other reactive sulfur compounds, hydrogen peroxide vapor,and strongly reducing materials. While antifoggants and stabilizers mayprotect, to some extent, against such effects, it is normally understoodthat antifoggants protect against spontaneous growth of fog duringprolonged storage or storage at high temperatures and humidities, orduring development to maximum contrast and speed, or both. It is knownthat photographic silver halide emulsions can be stabilized against'theharmful effects noted above by the addition of sulfinic or seleninicacids, or their watersoluble salts, as disclosed in Brunken US. Patent2,057,- 764, issued October 20, 1936. It is further known that thestabilizing effect of sulfinic or seleninic acids, or theirwater-soluble salts, can be improved by the addition of minute amountsof salts or esters of organic thiosulfonic acids. (Mueller US. Patent2,394,198, issued February 5. 1946.)

We have now found that certain esters of organic thiosulfonicacids havea marked stabilizing effect if substantial amounts thereof areincorporated in photographic silver halide emulsions. Contrasted withthis effect of the esters of organic thiosulfonic acids, the salts oforganic thiosulfonic acids have some stabilizing action, although theyare strong desensitizers for photographic silver halide emulsions whenemployed at concentrations approaching those at which the esters of ourinvention are employed. We have further found that when esters ofthiosulfonic acids are employed according to our invention, the additionof a sulfonate, such as sodium p-toluenesulfonate, does not improve thestabilization effect obtained, and in fact, frequently interferes withthe antifoggant properties of the esters of thiosulfonic acids.

The esters of organic thiosulfonic acids which can be 3,047,393 PatentedJuly 31, 1962 used in our invention include those represented by thefollowing general formula:

wherein R represents an alkyl group, such as methyl, ethyl, propyl,butyl, etc. (e.g., an alkyl group containing from 1 to 4 carbon atoms),or an aryl group, such as phenyl, tolyl, etc. (e.g., a monocyclic arylgroup of the benzene series containing from 6 to 7 carbon atoms) and Rrepresents an alkyl group, such as methyl, ethyl, propyl, butyl, etc.(e.g., an alkyl group containing from 1 to 4 carbon atoms), an arylgroup, such as phenyl, tolyl, etc. (e.g., a monocyclic aryl group of thebenzene series containing from 6 to 7 carbon atoms) or an aralkyl group,such as benzyl, B-phenethyl, etc. (e.g., an aralkyl group containingfrom 7 to 8 carbon atoms). The esters represented by Formula 1 abovehave sometimes been named as disulfoxides, in which case they can bewritten as conforming to the following general formula:

wherein R and R each have the values given above, although recent workby Cymerman and Willis (J. Chem. Soc., 1951, p. 1332) indicates that thedisulfoxide assignment is incorrect. I

Our invention also contemplates bis-esters of the type represented bythe following general formula:

wherein R has the values given above and R represents an alkylene group,such as ethylene, trimethylene (propylene), tetramethylene (butylene),methyl-substituted propylene, pentamethylene, hexylene, heptamethylene,decamethylene, etc. (e.g., an alkylene group containing from about 2 to10 carbon atoms). As in the case of the esters represented by Formula Iabove, the esters of Formula II can also be designated as sulfoxidederivatives, in which case they can be written as conforming to thefollowing general formula (see above comment under Formula Ia):

wherein R and R each have the values given above.

The radicals represented by R and R above can be further substituted byfunctional groups containing sulfur, oxygen, or nitrogen atoms, such asby hydroxyl, mercapto, amino, methylamino, anilino, methoxyl, ethoxyl,etc., as well as by halogen atoms, such as chlorine, bromine, etc.

Typical esters of organic thiosulfonic acids which can be used in ourinvention include, for example, the following:

(1) Ethane-1,2-bis(p-toluenethiosulfonate), R. Otto, Rossing, Ber., vol.20, p. 2088 (1887); ibid., vol. 25, p. 1478. (2) Propane 1,3bis(p-toluenethiosulfonate), I.C.A. Chivers, S. Smiles, Jour. Chem.Soc., 1928, p. 697. (3) Decane-1,10-bis(p-toluenethiosulfonate) (4)Pentane-1,5-bis (p-toluenethiosulfonate) (5 Benzylp-toluenethiosulfonate. (6) p-Tolyl p-toluenethiosulfonate. (7) Benzyl,ethanethiosulfonate. (8) Methyl methanethiosulfonate. (9) Methylethanethiosulfonate. (10) Ethyl methanethiosulfonate. 1 1 Butylethanethiosulfonate.

For the purposes of inhibiting fog formation, the thiosulfonic esters ofour invention can be added to the emulsion during the process ofmanufacture, either during mixing, ripening, of after-ripening, in orderto avoid loss of sensitivity and to inhibit the growth of fog with the 3passage of time under non-ideal conditions of storage.

The thiosulfonic esters can be added to the emulsions in the form oftheir solutions in a suitable innocuous solvent, such as ethanol,pyridine, dioxane, etc. While the concentration of a given thiosulfonicester will vary to some extent, depending upon the chemical nature ofthe thiosulfonic ester, its purity, type of silver halide emulsion,concentration of silver halide, etc., we have found that theconcentration of the thiosulfonic esters should be at least 0.05 g. permole of silver halide. The maximum amount of thiosulfonic ester willalso vary, although we have found, in general, that it can be as high asabout g. per mole of silver halide. These thiosulfonic esters can beadded to unsensitized, chemically sensitized or optically sensitizedphotographic emulsions and while the effects are not substantial whensensitivity and fog measurements are made soon after coating (exceptwith prolonged or forced development where fog is strongly diminished),the efiect of these compounds becomes quite apparent after anappreciable interval of time upon storage at elevated temperatures anddry or somewhat humid conditions.

The preparation of silver halide emulsions involves three separateoperations: (1) the emulsification and digestion or ripening of thesilver halide, (2) the freeing of the emulsion from excess solublesalts, usually by washing, and (3) the second digestion orafter-ripening to obtain increased sensitivity. (Mees, The Theory of thePhotographic Process (1952).) We prefer to add the fog-inhibiting agentsafter the final digestion or afterripening, although they canadvantageously be added prior to digestion.

If desired, the thiosulfonic esters of our invention can be incorporatedin the emulsions without adverse efiects by the bathing techniques knownto those skilled in the art.

The photographic emulsions used in practicing our invention are of thedeveloping-out type.

The emulsions can be chemically sensitized by any of the acceptedprocedures. The emulsions can be digested with naturally active gelatin,or sulfur compounds can be added such as those described in SheppardU.S. Patent 1,574,944, issued March 2, 1926, Sheppard et al. U.S. Patent1,623,499, issued April 5, 1927, and Sheppard et al. U.S. Patent2,410,689, issued November 5, 1946.

The emulsions can also be treated with salts of the noble metals such asruthenium, rhodium, palladium, iridium, and platinum. Representativecompounds are ammonium chloropalladate, potassium chloroplatinate, andsodium chloropalladite, which are used for sensitizing in amounts belowthat which produces any substantial fog inhibition, as described inSmith and Trivelli U.S. Patent 2,448,060, issued August 31, 1948.

The emulsions can also be chemically sensitized with gold salts asdescribed in Waller et al. U.S. Patent 2,399,- 083, issued April 23,1946, or stabilized with gold salts as described in 'Damschroder U.S.Patent 2,597,856, issued May 27, 1952, and Yutzy and Leermakers U.S.Patent 2,597,915, issued May 27, 1952. Suitable compounds are potassiumchloroaurite, potassium aurithiocyanate, potassium chloroaurate, aurictrichloride and 2-aurosulfo benzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agentssuch as stannous salts (Carroll U.S. Patent 2,487,850, issued November15, 1949), polyamines, such as diethylene triamine (Lowe and Jones U.S.Patent 2,- 518,698, issued August 15, 1950), polyamines, such asspermine (Lowe and Allen U.S. Patent 2,521,925, issued September 12,1950), or bis(fl-aminoethyl) sulfide and its water-soluble salts (Loweand Jones U.S. Patent 2,521,- 926, issued September 12, 1950).

The emulsions can also be optically sensitized with cyanine andmerocyanine dyes, such as those described in Brooker U.S. Patents1,846,301, issued February 23, 1932; 1,846,302, issued February 23,1932; and 1,942,854,

issued January 9, 1934; White U.S. Patent 1,990,507, issued February 12,1935; Brooker and White U.S. Patents 2,112,140, issued March 22, 1938;2,165,338, issued July 11, 1939; 2,493,747, issued January 10, 1950 and2,739,- 964, issued March 27, 1956; Brooker and Keyes U.S. Patent2,493,748, issued January 10, 1950; Sprague U.S. Patents 2,503,776,issued April 11, 1950, and 2,519,001, issued August 15, 1950; Heseltineand Brooker U.S. Patent 2,666,761, issued January 19, 1954; HeseltineU.S. Patent 2,734,900, issued February 14, 1956; Van Lare U.S. Patent2,739,149, issued March 20, 1956; and Kodak Limited British Patent450,958, accepted July 15, 1936.

The emulsions may also contain speed increasing compounds of thequaternary ammonium type of Carroll U.S. Patent 2,271,623, issuedFebruary 3, 1942; Carroll and Allen U.S. Patent 2,288,226, issued June30, 1942; and Carroll and Spence U.S. Patent 2,334,864, issued November23, 1943; and the polyethylene glycol type of Carroll and Beach U.S.Patent 2,708,162, issued May 10, 1955; or the thiopolymers of Graham andSagal U.S. application Serial No. 799,839, filed December 12, 8, or Dannand Chechak U.S. application Serial No. 779,874, filed December 12,1958, or the quaternary ammonium salts and polyethylene glycols of PiperU.S. Patent 2,886,437, issued May 12, 1959.

The emulsions may contain a suitable gelatin plasticizer such asglycerin; a dihydroxy alkane such as 1,5-pentane diol as described inMilton and Murray U.S. application Serial No. 588,951, filed June 4,1956 (now U.S. Patent No. 2,960,404, issued November 15, 1960); an esterof an ethylene bis-glycolic acid such as ethylene bis(methyl glycolate)as described in Milton U.S. application Serial No. 662,564, filed May31, 1957 (now U.S. Patent No. 2,904,434, issued September 15, 1959);bis-(ethoxy diethylene glycol) succinate as described in Gray U.S.application Serial No. 604,333, filed August 16, 1956 (now U.S. PatentNo. 2,940,854, issued June 14, 1960), or a polymeric hydrosol as resultsfrom the emulsion poly merization of a mixture of an amide of an acid ofthe acrylic acid series, an acrylic acid ester and a styrenetypecompound as described in Tong U.S. Patent 2,852,- 386, issued September16, 1958. The plasticizer may be added to the emulsion before or afterthe addition of a sensitizing dye, if used The emulsions may be hardenedwith any suitable hardener for gelatin such as formaldehyde; ahalogensubstituted aliphatic acid such as mucobromic acid as describedin White U.S. Patent 2,080,019, issued May 11, 1937; a compound having aplurality of acid anhydride groups such as 7,8-diphenylbicyclo(2,2,'2)-7-octene- 2,3,5,6-.tetra-car-boxylic dianhydride, or adicarboxylic or a disulfonic acid chloride such as terephthaloylchloride or naphthalene-1,S-disulfonyl chloride as described in Allenand Carroll U.S. Patents 2,725,294, and 2,725,295, both issued November29, 1955; a cyclic 1,2-diketone such as cyclopentane-1,2-dione asdescribed in Allen and Byers U.S. Patent 2,725,305, issued November 29,1955; a bisester of methane-sulfonic acid such as1,2-di-(methanesulfionoxy)-ethane as described in Allen and Laakso U.S.Patent 2,726,162, issued December 6, 1955;1,3-dihydroxymethylbenzirnidazol-2-one as described in July, K-nott andPollak U.S. Patent 2,732,316, issued January 24, 1956; a dialdehyde or asodium bisulfite derivative thereof, the aldehyde groups of which areseparated by 23 carbon atoms, such as B-methyl glutaraldehyde bissodiumbisulfite as described in Allen and Bur-ness U.S. patent applicationSerial No. 556,031, filed December 29, 1955 (now abandoned); abis-aziridine carboxamide such as trimethylene bis(1-aziridinecarboxarnide) as described in Allen and Webster U.S. patent applicationSerial No. 599,891, filed July 25, 1956 (now U.S. Patent 2,950,197,issued August 23, 1960); or 2,3-dihydroxy dioxane as described inJeffreys U.S. Patent 2,870,013, issued January 20, 1959.

The emulsions may contain a coating aid such as saponin; a lauryl oroleyl monoether of polyethylene glycol as described in Knox and DavisUS. Patent 2,831,766, issued April 22, 1958; a salt of a sulfiated andalkylated polyethylene glycol ether as described in Knox and Davis U.S.Patent 2,719,087, issued September 27, 1955; an acylated alkyl taur-inesuch as the sodium salt of N-oleoyl- N-methyl taurine as described inKnox, T wardokus and Davis U.S. Patent 2,739,891, issued March 27, 1956;the reaction product of a dianhydride of tetracarboxybut-ane with analcohol or an aliphatic amine containing from 8 to 18 carbon atoms whichis treated with a base, for example, the sodium salt of the monoester oftetracarboxybutane as described in Knox, Stenberg and Wilson U.S. Patent2,843,487, issued July 15, 1958; a watersoluble maleopimarate or amixture of a water-soluble maleopimarate and a substituted glutamatesalt as described in Knox and Fowler U.S. Patent 2,823,123, issuedFebruary 11, 1958; an alkali metal salt of a substituted amino acid suchas disodium N-(carbop-tert. octylphenoxypentaethoxy)glutamate asdescribed in Knox and Wilson U.S. patent application Serial No. 600,679,filed July 30, 195 6; or a sulfosuccinamate such as tetrasodiumN-(1,2-d-icarboxyethyl)-N-octadecyl sulfosuccin-amate or N lauryldisodium sulfosuccinamate as described in Knox and Stenberg U.S. patentapplication Serial No. 691,125, filed October 21, 1957 (now U.S. Patent2,992,108, issued July 11,1961).

The addenda which we have described may be used in various kinds ofphotographic emulsions. being useful in X-ray and other nonopticallysensitized emulsions they may also be used in orthochromatic,panchromatic, and infrared sensitive emulsions. They may be added to theemulsion before or after any sensitizing dyes which are used. Varioussilver salts may be used as the sensitive salt such as silver bromide,silver iodide, silver chloride, or mixed silver halides such as silverchlo-robromide or silver bromoiodide. The agents may be used inemulsions intended for color photography, for example, emulsionscontaining color-forming couplers or emulsions to be developed bysolutions containing couplers or other color-generating materials,emulsions of the mixed-packet type, such as described in Godowsky U.S.Patent 2,698,794, issued January 4, 1955; or emulsions of themixed-grain type, such as described in Carroll and Hanson U.S. Patent2,592,243, issued April 8, 1952. These agents can also be used inemulsions which form latent images predominantly on the surface of thesilver halide crystal or in emulsions which form latent imagespredominantly inside the silver halide crystal, such as those describedin Davey and Kno-tt U.S. Patent 2,592,250, issued April 8, 1952.

These may also be used in emulsions intended for use in diffusiontransfer processes which utilize the undeveloped silver halide in thenonimage areas of the negative to form a positive by dissolving theundeveloped silver halide and precipitating it on a receiving layer inclose proximity to the original silver halide emulsion layer. Suchprocesses are described in Rott U.S. Patent 2,352,014, issued June 20,1944, and Land U.S. Patents 2,584,029, issued January 29, 1952;2,698,236, issued December 28, 1954, and 2,543,181, issued February 27,1951; and Yackel et a1. U.S. patent application Serial No. 586,705,filed May 23, 1956 (now U.S. Patent 3,020,155, issued February 6, 1962).They may also be used in color transfer processes which utilize thediffusion transfer of an image-wise distribution of developer, coupleror dye, from a light-sensitive layer to a second layer, while the twolayers are in close proximity to one another. Color processes of thistype are described in Land U.S. Patents 2,559,643, issued July 10, 1951,and 2,698,798, issued January 4, .1955; Land and Rogers Belgian Patents554,933 and 554,934, granted August 12, 1957; International PolaroidBelgian Patents 554,212, granted July 16, 1957, and 554,935, grantedAugust 12, 1957; Yutzy U.S. Patent 2,756,142, granted July 24, 1956,

6 and Whitrnore and Mader U.S. patent application Serial No. 734,141,filed May 9, 1958.

In the preparation of the silver halide dispersions employed forpreparing silver halide emulsions, there may be employed as thedispersing agent for the silver halide in its preparation, gelatin orsome other colloidal material such as colloidal alburnin, a cellulosederivative, or a synthetic resin, for instance, a polyvinyl compound.Some colloids which may be used are polyvinyl alcohol or a hydrolyzedpolyvinyl acetate as described in Lowe U.S. Patent 2,286,215, issuedJune 16, 1942; a far hydrolyzed cellulose ester such as celluloseacetate hydrolyzed to an acetyl content of 1926% as described in U.S.Patent 2,327,808 of Lowe and Clark, issued August 24, 1943; awater-soluble ethanolamine cellulose acetate as described in Yutzy U.S.Patent 2,322,085, issued June 15, 1943; a polyacrylamide having acombined acrylimide content of 1520% and a specific viscosity of 0.09-0.225 or an imidized polyacrylamide having a combined acrylimide contentof 60%, a combined acrylic acid content of 412% and a specific viscosityof .251.5 as described in Lowe, Minsk and Kenyon U.S. Patent 2,541,474,issued February 13, 1951; zein as described in Lowe U.S. Patent2,563,791, issued August 7, 1951; a vinyl alcohol polymer containingurethane carboxylic acid groups of the type described in Unruh and SmithU.S. Patent 2,768,154, issued October 23, 1956; or containingcyano-acetyl groups such as the vinyl alcohol- In addition to vinylcyanoacetate copolymer as described in Unruh, Smith and Priest U.S.Patent 2,808,311, issued October 1, 195 7; or a polymeric material whichresults from polymerizing a protein or a saturated acylated protein witha monomer having a vinyl group as described in U.S.

Patent 2,852,382, of Illingsworth, Dann and Gates, issued September 16,1958.

If desired, compatible mixtures of two or more of these colloids may beemployed for dispersing the silver halide in its preparation.Combinations of these antifoggants, sensitizers, hardeners, etc., may beused.

The following examples will serve to illustrate more fully the usefulstabilizing effects of many of the thiosulfonic esters useful inpracticing our invention. A series of coatings were made on an ordinaryphotographic film support, such as cellulose acetate, of an ordinaryphotographic negative speed bromiodide emulsion, both with and withoutthe addition of one of the esters of thiosulfonic acids at theconcentration shown in the following table. The esters were added fromsubstantially neutral solutions. The coatings were then dried andexposed on an intensity scale sensitometer (Kodak Type Ib) and developedfor 4 minutes at 68 F. in Kodak D-19 Developer or for 5 minutes in KodakDK-50 Developer. A separate set of coatings was incubated for one weekat F., constant relative humidity at about 50%, and in some cases fortwo weeks under the same conditions. These incubated coatings were thenexposed and processed in the same manner as the fresh coatings describedabove. The relative speeds and fogs for each of the coatings were thenmeasured. The relative speed is inversely proportional to the exposureto produce a density of 0.3 above fog.

In the following table the compound numbers correspond to the numbersused above for the specific thiosulfonic esters. In each coating series,the same emulsion batch was used, although different emulsion batcheswere used for certain of the coating series. Wherever a differentemulsion batch was used, a new control series was run for that batch toshow the degree of improvement obtained. Kodak Developer D-19 has thefollowing composition:

Water, about F. (50 C.) ccs 500 Elon developing agent grams 2.0 Sodiumsulfite, desiccated do 90.0

V 1 N -methyl-p-aminopheuol sulfate.

.7 Hydroquinone "do..-" 8.0 Sodium carbonate,monohydrated do 52.5Potassium bromide do 5.0

Cold water to make 1 liter.

Kodak Developer DK-50 has the following composition:

Cold Water to make 1 liter.

The results of these coating series are given in the following table:

alcohol was added dropwise, with good stirring, to the hot solution. Thereaction mixture was refluxed for 4 hours (after the addition had beencompleted) and filtered while still hot. Ethyl acetate (50 ml.) wasadded to the hot solution which was then cooled, and the solid productremoved by filtration. The material was recrystallized by dissolving inthe minimum amount of hot absolute alcohol, and adding one-half volumeof ethyl acetate. The material may also be recrystallized from methanol.The yield was 7.5 g., M.-P. 8889 C.

Analysis.-Calcd. for CHI-1340484: C, H, S, 24.9. Found: C, 56.1; H, 6.5;S, 24.7.

In like manner, other thiosulfonic esters can be prepared by using otherhalogenated alkanes in the above examples,

" or by using sulfinic acids as the starting material as described byHere and Smiles, J. Chem. Soc. 125, page 2359, 1924.

T ABLE Incubation- Incuba- Com- Fresh Coating 1 Week tion-2 CoatingDevelpound gjmole Weeks N 0. oper No. .AgX

Speed Fog Speed Fog Fog Control 100 12 76 25 1 0. 75 74 10 71 09 2 0. 7595 10 81 10 3 0. 3 89 11 107 16 3 3. 98 .11 102 .16 Control 100 08 19617 46 0. 45 89 .06 215 08 25 Control 100 13 64 33 79 6 0.15 80 .12 86.12 .30 0.15 86 12 78 16 .40 Control 100 .08 135 23 65 8 0.09 94 07 15509 18 9 0.38 89 07 115 09 .13 0. 38 89 .07 118 .10 .14

The thiosulfonic esters useful in practicing our invention can beprepared according to methods which have been previously described inthe prior art. For example, the monoesters of Formula I above canadvantageously be prepared by condensing an alkali metal thiosulfonatewith a halogen-substituted alkane. The bis-esters of Formula II can beprepared according to the same general method by condensing an alkalimetal thiosulfonate with a dihalogenated alkane. This general method ofpreparation is illustrated in the following examples:

Example 1 .Ethane-l ,2-Bis (p-Toluenethiosulfonate) 1,2-dibromoethane (9g., 0.048 mole) and sodium-(ptoluenethiosulfonate) g., 0.095 mole) in 70ml. of alcohol were refluxed for 5 hours. The hot reaction mixture wasfiltered and cooled. The solid product was removed by filtration andrecrystallized from absolute alcohol. The yield was 5 g., M.P. 73-75 C.

Analysis.Calcd. for C H O S C, 47.7; H, 4.8; S, 31.8. Found: C, 48.0; H,4.7; S, 31.8.

Example 2.Pr0pmze-],3-Bis (p-Toluenethiosulfonate)Sodium(p-toluenethiosulfonate) (21 g., 0.1 mole) was dissolved in 100ml. of alcohol and heated to reflux. 1,3- dibromopropane (10 g., 0.05mole) was added dropwisc, with good stirring, to the hot solution. Thereaction mixture was refluxed for 5 hours after addition had beencompleted. The hot reaction mixture was filtered and cooled. The solidproduct was removed by filtration. The mother liquors were concentratedto dryness for second-crop material. The product was recrystallized bydissolving in the minimum amount of hot absolute alcohol, and addingone-half volume of ethyl acetate. The solid product was removed byfiltration and dried. The yield was 10 g., M.P. 6567 C.

Example 3.Decane-1,10-Di- (p-Toluenethiosulfonate)Sodium(p-toluenethiosulfonate) (14 g., 0.066 mole) was dissolved in 80ml. of alcohol and heated to reflux. 1,10-dibromodecane (10 g., 0.033mole) in 20 ml. of

wherein R represents a member selected from the class consisting of analkyl group and an aryl group and R represents a member selected fromthe class consisting of an alkyl group, an aryl group and an aralkylgroup.

2. A photographic silver halide emulsion as defined in claim 1 whereinsaid photographic silver halide emulsion is a gelatino-silver-bromiodideemulsion.

3. A photographic silver halide emulsion stabilized by the additionthereto of from 0.05 to 10 g. per mole of silver halide of an esterselected from those represented by the following general formula:

wherein R represents a member selected from the class consisting of analkyl group and an aryl group and R represents an alkylene group.

4. A photographic silver halide emulsion as defined in claim 3 whereinsaid photographic silver halide emulsion is agelatino-silver-brorniodide emulsion.

5. A photographic silver halide emulsion stabilized by the additionthereto of from 0.05 to 10 g. per mole of silver halide of an esterselected from those represented by the following general formula:

RSO S--R wherein R and R each represents an aryl group.

9 6. A photographic silver halide emulsion stabilized by the additionthereto of from 0.05 to 10 g. per mole of silver halide of an esterselected from those represented by the following general formula:

wherein R and R each represents an alkyl group containing from l to 4carbon atoms.

7. A photographic silver halide emulsion stabilized by the additionthereto of from 0.05 to 10 g. per mole of silver halide of an esterselected from those represented by the following general formula:

10 the addition there-to of from 0.05 to 10 g. per mole of silver halideof methyl methanethiosulfonate.

10. A photographic silver halide emulsion stabilized by the additionthereto of from 0.05 to 10 g. per mole of silver halide of methylethanethiosulfonate.

11. A photographic silver halide emulsion stabilized by the additionthereto of from 0.05 to 10 g. per mole of silver halide ofdecane-l,lO-bis(p-toluenethiosulfonate).

12. A photognaphic silver halide emulsion stabilized by the additionthereto of from 0.05 to 10 g. per mole of silver halide of ethylmethanethiosulfonate.

13. A photographic silver halide emulsion stabilized by the additionthereto of from 0.05 to 10 g. per mole of silver halide ofpropane-l,3-bis(p-toluenethiosulfonate).

OTHER REFERENCES Glafkides Photographic Chemistry, vol. 1., pages379-380, Fountain Press (1958). Copy in Div. 60.

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION STABILIZED BY THE ADDITIONTHERETO OF FROM 0.05 TO 10 G. PER MOLE OF SILVER HALIDE OF AN ESTERSELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA:
 3. APHOTOGRAPHIC SILVER HALIDE EMULSION STABILIZED BY THE ADDITION THERETOOF FROM 0.05 TO 10 G. PER MOLE OF SILVER HALIDE OF AN ESTER SELECTEDFROM THOSE REPRESENTED BY THE FOLLOWING FORMULA: